1. Technical Field
The present invention relates to air filtration for semiconductor manufacturing facilities, general business, or residential use, and more specifically, to the use of a liquid to remove impurities from circulated air in these situations.
2. Description of the Related Art
Currently, air filtration for both commercial and residential applications is accomplished by passing the air through a mesh material that traps a large percentage of the particulate matter in the air. Depending on the particular mesh used, the effectiveness of the filtration can vary. The current state of the art in air filtration is High Efficiency Particulate Arresting (HEPA) filtration. HEPA filtration was developed during World War II by the Atomic Energy Commission as a means to protect their researchers from radioactive particles in the air. HEPA filters will remove particulate matter down to the range of 0.3 micron at an efficiency of 99.97%. HEPA filters have become widely known and used in recent years in settings as diverse as clean rooms for the manufacture of semiconductor chips, hospital operating rooms, and home air cleaners for allergy and asthma sufferers.
However, as the filter becomes clogged with the captured materials, the flow of air through the filter becomes more restricted, while the fans used to circulate the air have to work harder. Periodically, either the filter must be replaced with a new filter or it must be removed, cleaned, and reinstalled. Many filters, such as HEPA filters, cannot be cleaned and reused. Throw away filters contribute to the ever-growing waste disposal problem, but cleaning and reusing the filters tends to degrade the filters over time to a point of ruin.
Air filtration systems utilizing a liquid to aid in removal of particulate matter or toxic gases have been introduced for use in specific activities that generate high levels of polluted air. One example is U.S. Pat. No. 5,408,834, which scrubs air from such sources as a spray-painting booth, resulting in an air stream that is heavily polluted with volatile organic compounds. This patent directs the air into a series of chambers where the air contacts a liquid containing active microbes that will convert the organic compounds into non-toxic substances. One chamber sprays the incoming air with a spray to cool the air to a proper temperature for the microbes to work. Then, in order to increase the contact between the polluted air and the microbial laden liquid, one chamber sprays the liquid over a filter medium, through which the air must pass.
A somewhat similar problem is faced in the use of vacuum cleaners, where it is desirable to clean a stream of very dirty air before it leaves the vacuum cleaner. One current solution is to pass the air stream through a container of water, where turbulence mixes the air and water, so that the collected dirt is transferred from the air to the water, where it may be disposed of.
It would be desirable to have an air filtration system that did not create waste, yet remained efficient. It would further be desirable if such an air filtration system was suitable for use in clean-rooms, such as for the manufacture of semiconductors, as well as in residential and other commercial uses.
The invention includes a device and a method for air filtration, using a liquid, rather than a mesh, to remove particulate matter from the air. The invention also provides for the removal of other contaminants, such as solvents, toxic gasses, or other fumes. All contaminants would be trapped in the liquid, from which they can be removed by current methods, such as centrifugal force, allowing the liquid to be reused. The specific embodiment of the filtration system can use water or another liquid, or multiple different liquids to remove the contaminants. Bubblers, sprays, and vapors are a few of the ways in which the air/liquid interface can be structured.